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Keypad membrane, substitution by ic's possible ??
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coromonadalix:
I have an 5 rows by 8 cols membrane (keypad of 38 buttons) whos dying and i want to substitute it by technology for future automation by a future HMI interface module from DWIN.
Ie : switching ic's, and a serial (rs232 level max232) slave kinda look a like arduino if possible ...
The rows are pulled high (+5v) by 100k resisstors and goes thru a 74hc244
The cols are going to an 74hc374
There is no signal diode or anything else in the keypad circuit
I'm poor at coding, searching for similar projects, ideas, codes snippets ??
I'll check the specs to know if it will or could talk back on the serial (acknowledge, command echoing etc .. )
For a keypad substitute, a guy at my job is searching for custom made one(s) ... but eventually i'll have to put something in parallel with the keyboard.
Can it be done ?
thks
coromonadalix:
Answered my own questions
http://www.arduinoforum.nl/viewtopic.php?f=6&t=1923&start=10#p15323
Using an AD75019 but they are pricey 38$ a piece outch
oPossum:
Do you need more than one key at a time?
A pair of 74HC4051 will do [any] one key. Special keys like shift can be done with 1/4 of a 74HC4066.
coromonadalix:
nope just a push of a single switch, and two switches who may need to be pushed 1-3 seconds long.
Found many "crosspoint switches" parts at Mitel, Hynix, Renesas, Analog device, etc ... literally tons of fake from china
Found arduino and avr code snippets, will try to implement a solution with an arduino
I did not knew the "crosspoint switches" terms, thats why i have posted here :(
Gonna try to play with Mitel mt8808 and mt8816 they cost around 10-12$ each, an AD75019 is 40-50$ a piece loll
thks for the 4051 tips it may prove useful too
Someone:
https://www.eevblog.com/forum/beginners/simulate-a-matrix-keypad-with-a-microcontroller/
or offsite:
https://www.avrfreaks.net/forum/reverse-matrix-keyboard-emulate-it
Many cheap micro controllers can do this without any external hardware. But unless the comms channel is extremely slow you need a software architecture that is non blocking on either the communications channel or the matrix emulation.
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